Circuitry related to Hall effect devices and other magnetic field circuitry has been developed for a variety of purposes. U.S. Pat. No. 4,156,191, issued to Knight, et al. on May 22, 1979, discloses an apparatus for adjusting the magnetic coupling between a Hall effect device and an operating magnet. U.S. Pat. No. 4,190,799, issued to Miller, et al. on Feb. 26, 1980, discloses a method for measuring the magnitude and sign of the Hall angle of the material of a wafer. U.S. Pat. No. 4,270,087, issued to A. K. Littwin on May 26, 1981, discloses an apparatus for testing permanent magnets using electromagnets and Hall sensors. U.S. Pat. No. 4,084,135, issued to R. S. Enabnit on Apr. 11, 1978, discloses a system and method for checking the sensitivity and performance of an electromagnetic field variation detector. And, U.S. Pat. No. 4,230,987, issued to G. Mordwinkin on Oct. 28, 1980, discloses a digital eddy current apparatus for generating metallurgical signatures and monitoring metallurgical contents of an electrically conductive material.
While the circuits disclosed in these patents are related to magnetic field or Hall effect devices, none of these patents discloses a method for monitoring the tolerance of the operate and release levels of a Hall effect device.
A circuit which does test the operate and release times of a Hall effect device is the subject of a U.S. patent application also titled, "Hall Effect Device Test Circuit". That application was filed in the U.S. patent office on Aug. 30, 1982, and was assigned Ser. No. 412,758. The circuit disclosed in that application utilizes a novel arrangement of relays and retriggerable monstable multivibrators, rather than the integrated circuit arrangement of the present invention.
Accordingly, it is the object of the present invention to provide a novel test circuit to monitor the operate and release levels of a Hall effect device. Features of the present invention include high reliability, minimum complexity and visual indications of tolerable operate and release levels.